Semiconductor device and method for fabricating the same

ABSTRACT

A method for fabricating a capacitor includes: forming a bottom electrode; forming a dielectric layer on the bottom electrode; forming a metal oxide layer including a metal having a high electronegativity on the dielectric layer; forming a sacrificial layer on the metal oxide layer to reduce the metal oxide layer to a metal layer; and forming a top electrode on the sacrificial layer to convert the reduced metal layer into a high work function interface layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/002,866 filed on Jun. 7, 2018 which claims benefits of priority ofKorean Patent Application No. 10-2017-0160654 filed on Nov. 28, 2017.The disclosure of each of the foregoing application is incorporatedherein by reference in its entirety.

BACKGROUND 1. Field

Exemplary embodiments of the present invention relates generally to asemiconductor device and a method for fabricating the same. Moreparticularly, the present invention relates to a semiconductor deviceincluding a capacitor and a method for fabricating the semiconductordevice.

2. Description of the Related Art

A capacitor of a semiconductor device may include a bottom electrode, adielectric layer, and a top electrode. As the degree of integration of asemiconductor device increases, the thickness of the dielectric layerdecreases which may result in increased leakage current. Increasing thethickness of the dielectric layer to reduce the leakage current leads toan increase in the equivalent oxide layer thickness (T_(ox)).

SUMMARY

Exemplary embodiments of the present invention are directed to asemiconductor device including a capacitor which has improved leakagecurrent characteristics, and a method for fabricating the semiconductordevice.

In accordance with an embodiment of the present invention, a method forfabricating a capacitor includes: forming a bottom electrode; forming adielectric layer on the bottom electrode; forming a metal oxide layerincluding a metal having a high electronegativity on the dielectriclayer; forming a sacrificial layer on the metal oxide layer to reducethe metal oxide layer to a metal layer; and forming a top electrode onthe sacrificial layer to convert the reduced metal layer into a highwork function interface layer.

The forming of the sacrificial layer on the metal oxide layer may beperformed under a hydrogen gas atmosphere.

The forming of the sacrificial layer on the metal oxide layer mayinclude: forming a silicon layer on the metal oxide layer using ahydrogen-containing silicon source gas under a hydrogen gas atmosphere.

The forming of the sacrificial layer on the metal oxide layer mayinclude: forming a doped silicon layer on the metal oxide layer using ahydrogen-containing silicon source gas and a hydrogen-containing dopantgas under a hydrogen gas atmosphere.

The forming of the sacrificial layer on the metal oxide layer mayinclude: forming a silicon oxide layer on the metal oxide layer; andforming a silicon layer on the silicon oxide layer using ahydrogen-containing silicon source gas under a hydrogen gas atmosphere.

The forming of the silicon oxide layer on the metal oxide layer mayinclude: forming a laminate structure by alternatively depositing themetal oxide layer and the silicon oxide layer.

The forming of the top electrode on the sacrificial layer may include:forming a silicon germanium layer doped with an impurity on thesacrificial layer.

The forming of the top electrode on the sacrificial layer may beperformed at a temperature such that the sacrificial layer and thereduced metal layer react to form a metal silicide layer or a metalgermanide.

The metal oxide layer may include a nickel oxide, the reduced metallayer may include a nickel layer, and the high work function interfacelayer may include a nickel silicide or a nickel-rich nickel silicide.

The metal oxide layer may include a cobalt oxide, the reduced metallayer may include a cobalt layer, and the high work function interfacelayer may include a cobalt silicide or a cobalt-rich cobalt silicide.

The metal oxide layer may include a tungsten oxide, the reduced metallayer may include a tungsten layer, and the high work function interfacelayer may include a tungsten silicide or a tungsten-rich silicide.

The forming of the sacrificial layer on the metal oxide layer mayinclude: forming a germanium layer on the metal oxide layer using ahydrogen-containing germanium source gas under a hydrogen gasatmosphere.

The forming of the sacrificial layer on the metal oxide layer mayinclude: forming a doped germanium layer on the metal oxide layer usinga hydrogen-containing germanium source gas and a hydrogen-containingdopant gas under a hydrogen gas atmosphere.

The forming of the sacrificial layer on the metal oxide layer mayinclude: forming a germanium oxide layer on the metal oxide layer; andforming a germanium layer on the germanium oxide layer using ahydrogen-containing germanium source gas under a hydrogen gasatmosphere.

The forming of the germanium oxide layer on the metal oxide layer mayinclude: forming a laminate structure by alternatively depositing themetal oxide layer and the germanium oxide layer.

The metal oxide layer may include a nickel oxide, the reduced metallayer may include a nickel layer, and the high work function interfacelayer may include a nickel germanide.

The metal oxide layer may include a cobalt oxide, the reduced metallayer may include a cobalt layer, and the high work function interfacelayer may include a cobalt germanide.

The metal oxide layer may include a tungsten oxide, the reduced metallayer may include a tungsten layer, and the high work function interfacelayer may include a tungsten germanide.

The dielectric layer may include a zirconium oxide, an aluminum oxide,or a combination thereof.

The bottom electrode may include a titanium nitride, and the topelectrode may include a boron-doped silicon germanium layer.

In accordance with an embodiment of the present invention, a capacitorincludes: a bottom electrode; a dielectric layer formed on the bottomelectrode; a high work function interface layer formed on the dielectriclayer; and a top electrode including a silicon germanium layer formed onthe high work function interface layer, wherein the high work functioninterface layer includes a silicide having a high electronegativity or agermanide having a high electronegativity.

The high work function interface layer may include a nickel silicide ora nickel-rich nickel silicide.

The high work function interface layer may include a cobalt silicide, acobalt-rich cobalt silicide, a tungsten silicide, or a tungsten-richtungsten silicide.

The high work function interface layer may include a nickel germanide, acobalt germanide, or a tungsten germanide.

The top electrode may include a boron-doped silicon germanium layer.

The dielectric layer may include a zirconium oxide, an aluminum oxide,or a combination thereof.

The bottom electrode may have a cylindrical shape or a pillar shape.

The bottom electrode may include a titanium nitride.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of a semiconductor device inaccordance with an embodiment of the present invention.

FIGS. 1B and 1C are cross-sectional views of a capacitor as anapplication example of the semiconductor device in accordance with anembodiment of the present invention.

FIGS. 2A to 2D are cross-sectional views illustrating an example of amethod for fabricating the semiconductor device in accordance with anembodiment of the present invention.

FIGS. 3A to 3C are cross-sectional views illustrating another example ofa method for fabricating the semiconductor device in accordance with anembodiment of the present invention.

FIGS. 4A to 4C are cross-sectional views illustrating yet anotherexample of a method for fabricating the semiconductor device inaccordance with an embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a laminate structure of anickel oxide and a silicon oxide.

FIG. 6A is a cross-sectional view of a semiconductor device inaccordance with an embodiment of the present invention.

FIG. 6B is a cross-sectional view of a capacitor as an applicationexample of the semiconductor device in accordance with an embodiment ofthe present invention.

FIGS. 7A and 7B are cross-sectional views illustrating an example of amethod for fabricating the semiconductor device in accordance with anembodiment of the present invention.

FIGS. 8A to 8C are cross-sectional views illustrating another example ofa method for fabricating the semiconductor device in accordance with anembodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a laminate structure of anickel oxide and a germanium oxide,

FIGS. 10A to 10E are cross-sectional views illustrating a method forfabricating a DRAM capacitor in accordance with embodiments of thepresent invention.

FIG. 11 is a cross-sectional view of the DRAM capacitor in accordancewith an embodiment of the present invention.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the present invention tothose skilled in the art. Throughout the disclosure, like referencenumerals refer to like parts throughout the various figures andembodiments of the present invention.

The drawings are not necessarily to scale and in some instances,proportions may have been exaggerated in order to clearly illustratefeatures of the embodiments. When a first layer is referred to as being“on” a second layer or “on” a substrate, it not only refers to a casewhere the first layer is formed directly on the second layer or thesubstrate but also a case where a third layer exists between the firstlayer and the second layer or the substrate.

Hereafter, the embodiments of the present invention are described indetail. To simplify the description, a Dynamic Random Access Memory(DRAM) device is taken as an example, but the concept and spirit of thepresent invention are not limited to the DRAM only, and they may beapplied to other memory devices or semiconductor devices.

The embodiments described below are directed to an interface layer and atop electrode having a high work function of approximately 4.9 eV orhigher while preventing a reduction of a dielectric layer.

FIG. 1A is a cross-sectional view of a semiconductor device 100 inaccordance with an embodiment of the present invention.

Referring to FIG. 1A, the semiconductor device 100 may include a firstconductive layer 101, a dielectric layer 102, and a second conductivelayer 103.

The first conductive layer 101 may be formed of a silicon-containingmaterial and/or a metal-containing material. For example, the firstconductive layer 101 may be or include polysilicon, a metal, a metalnitride, a conductive metal oxide or combinations thereof. In someembodiments, the first conductive layer 101 may be or include dopedpolysilicon, titanium (Ti), a titanium nitride (TiN), a tantalum nitride(TaN), tungsten (W), a tungsten nitride (WN), ruthenium (Ru), iridium(Ir), a ruthenium oxide, an iridium oxide or combinations thereof.

The dielectric layer 102 may be formed of a high-k material. Thedielectric layer 102 may be or include a high-k material having adielectric constant that is higher than the dielectric constant of asilicon oxide. Examples of suitable high-k materials may include ahafnium oxide (HfO₂), a zirconium oxide (ZrO₂), an aluminum oxide(Al₂O₃), a titanium oxide (TiO₂), a tantalum oxide (Ta₂O₅), a niobiumoxide (Nb₂O₅) or a strontium titanium oxide (SrTiO₃). According toanother embodiment of the present invention, the dielectric layer 102may be a composite layer including two or more layers made of a high-kmaterial. According to an embodiment of the present invention, thedielectric layer 102 may be formed of a zirconium oxide-based materialhaving fine leakage current characteristics while sufficientlydecreasing an equivalent oxide layer thickness. For example, in someembodiments the dielectric layer 102 may be or include a ZAZ(ZrO₂/Al₂O₃/ZrO₂) or a ZAZA (ZrO₂/Al₂O₃/ZrO₂/Al₂O₃). According to otherembodiments of the present invention, the dielectric layer 102 may be orinclude a HAH (HfO₂/Al₂O₃/HfO₂). According to yet other embodiments ofthe present invention, the dielectric layer 102 may be or include one ofthe following multi-layer structures TiO₂/ZrO₂/Al₂O₃/ZrO₂,TiO₂/HfO₂/Al₂O₃/HfO₂, Ta₂O₅/ZrO₂/Al₂O₃/ZrO₂ or Ta₂O₅/HfO₂/Al₂O₃/HfO₂.

The second conductive layer 103 may be formed of a non-metal material.For example, the second conductive layer 103 may be formed of asilicon-containing material, a germanium-containing material or acombination thereof. In some embodiments, the second conductive layer103 may include a silicon (Si) layer, a germanium (Ge) layer, a silicongermanium (SiGe) layer or combinations thereof. In some embodiments, thesecond conductive layer 103 may have a multi-layer structure (SiGe/Si)formed by stacking the silicon germanium layer on the silicon layer. Inother embodiments, the second conductive layer 103 may have amulti-layer structure (SiGe/Ge) formed by stacking the silicon germaniumlayer on the germanium layer.

An interface layer 104 may be formed between the dielectric layer 102and the second conductive layer 103. The interface layer 104 may beformed of a conductive material. The interface layer 104 may be orinclude a high work function material. The interface layer 104 may bequalified as a “high work function interface layer.” For example, theinterface layer 104 may include a metal silicide. The interface layer104 may include a silicide whose electronegativity is high. In someembodiments, the interface layer 104 may include a nickel silicide, acobalt silicide or a tungsten silicide.

A stack structure of the first conductive layer 101, the dielectriclayer 102, the interface layer 104 and the second conductive layer 103may become a capacitor.

FIG. 1B is a cross-sectional view of a capacitor 100M as an applicationexample of the semiconductor device in accordance with an embodiment ofthe present invention.

Referring to FIG. 1B, the capacitor 100M may include a bottom electrode101M, a dielectric layer 102M, an interface layer 104M, and a topelectrode 103M.

The bottom electrode 101M may be formed of a metal nitride. For example,the bottom electrode 101M may be formed, for example, of a titaniumnitride (TiN).

The top electrode 103M may be formed, for example, of a silicongermanium (SiGe) layer. The silicon germanium layer may be doped with adopant, for example, boron.

The dielectric layer 102M may have a ZAZ (ZrO₂/Al₂O₃/ZrO₂) stackstructure. The dielectric layer 102M may include a first zirconium oxide102A, an aluminum oxide 102B and a second zirconium oxide 102C which aresequentially stacked. The dielectric layer 102M may further include analuminum oxide 102D formed on the second zirconium oxide 102C. Thisstructure is referred to as a ZAZA stack structure. The aluminum oxide102D, which is a material with a large bandgap, may improve a leakagecurrent. According to another embodiment, SiO₂ may be employed as alarge bandgap material instead of aluminum oxide 102D.

The interface layer 104M may be formed, for example, a nickel silicide(Ni-Silicide).

FIG. 1C is a cross-sectional view of a capacitor 100M′ as an applicationexample of the semiconductor device in accordance with an embodiment ofthe present invention.

Referring to FIG. 1C, the capacitor 100M′ may include a bottom electrode101M, a dielectric layer 102M, an interface layer 104M′, and a topelectrode 103M. Hence, the capacitor 100M′ may be identical to thecapacitor 100M of FIG. 1B except for the interface layer 104M′.Specifically, the bottom electrode 101M may be formed of a metalnitride. For example, the bottom electrode 101M may be formed, forexample, of a titanium nitride (TiN).

The top electrode 103M may be formed, for example, of a silicongermanium (SiGe) layer. The silicon germanium layer may be doped with adopant, for example, boron.

The dielectric layer 102M may have a ZAZ (ZrO₂/Al₂O₃/ZrO₂) stackstructure. The dielectric layer 102M may include a first zirconium oxide102A, an aluminum oxide 102B and a second zirconium oxide 102C which aresequentially stacked. The dielectric layer 102M may further include analuminum oxide 102D formed on the second zirconium oxide 102C. Thisstructure is referred to as a ZAZA stack structure. The aluminum oxide102D, which is a material with a large bandgap, may improve a leakagecurrent. According to another embodiment, SiO₂ may be employed as alarge bandgap material instead of aluminum oxide 102D.

The interface layer 104M′ may include a nickel-rich nickel silicide(Ni-rich Ni-Silicide). The nickel-rich nickel silicide refers to anickel silicide where the number of nickel atoms is greater than thenumber of silicon atoms. For example, nickel-rich nickel silicideinclude Ni₃Si, Ni₂Si, and Ni₃Si₂.

FIGS. 2A to 2D are cross-sectional views illustrating an example of amethod for fabricating the semiconductor device 100 in accordance withan embodiment of the present invention.

Referring to FIG. 2A, a first conductive layer 11 may be formed. Thefirst conductive layer 11 may be formed of a silicon-containing materialand/or a metal-containing material. For example, the first conductivelayer 11 may include polysilicon, a metal, a metal nitride, a conductivemetal oxide or combinations thereof. In some embodiments, the firstconductive layer 11 may include doped polysilicon, titanium (Ti), atitanium nitride (TiN), a tantalum nitride (TaN), tungsten (W), atungsten nitride (WN), ruthenium (Ru), iridium (Ir), a ruthenium oxide,an iridium oxide, etc. In an embodiment, the first conductive layer 11may be formed, for example, by Chemical Vapor Deposition (CVD), AtomicLayer Deposition (ALD) or any other suitable method.

A dielectric layer 12 may be formed on the first conductive layer 11.The dielectric layer 12 may be formed of a high-k material. Thedielectric layer 12 may be formed of a high-k material having adielectric constant that is higher than the dielectric constant of asilicon oxide. In some embodiments, the dielectric layer 12 may includea hafnium oxide (HfO₂), a zirconium oxide (ZrO₂), an aluminum oxide(Al₂O₃), a titanium oxide (TiO₂), a tantalum oxide (Ta₂O₅), a niobiumoxide (Nb₂O₅) or a strontium titanium oxide (SrTiO₃). According toanother embodiment of the present invention, the dielectric layer 12 maybe a composite layer including two or more layers of the aforementionedhigh-k materials. According to an embodiment of the present invention,the dielectric layer 12 may be formed of a zirconium oxide-basedmaterial having fine leakage current characteristics while sufficientlyreducing an equivalent oxide layer thickness. For example, thedielectric layer 12 may include a ZAZ (ZrO₂/Al₂O₃/ZrO₂) or a ZAZA(ZrO₂/Al₂O₃/ZrO₂/Al₂O₃) structure. According to another embodiment ofthe present invention, the dielectric layer 12 may include a HAH(HfO₂/Al₂O₃/HfO₂) structure. According to yet another embodiment of thepresent invention, the dielectric layer 12 may be one of the followingmulti-layer structures TiO₂/ZrO₂/Al₂O₃/ZrO₂, TiO₂/HfO₂/Al₂O₃/HfO₂,Ta₂O₅/ZrO₂/Al₂O₃/ZrO₂ or Ta₂O₅/HfO₂/Al₂O₃/HfO₂.

Referring to FIG. 2B, a sacrificial interface layer 13 may be formed onthe dielectric layer 12. The sacrificial interface layer 13 may includean easily-reduced chemical species of oxide. The sacrificial interfacelayer 13 may include a chemical species of oxide whose electronegativityis high. The sacrificial interface layer 13 may include aneasily-reduced chemical species of oxide whose electronegativity ishigh. The sacrificial interface layer 13 may be 2 nm or less inthickness D1.

According to an embodiment of the present invention, the sacrificialinterface layer 13 may include an easily-reduced metal oxide whoseelectronegativity is high. For example, the sacrificial interface layer13 may be a nickel-containing layer. In an embodiment, the sacrificialinterface layer 13 may include an oxide containing nickel, i.e., anickel oxide (NiO). The electronegativity of nickel may be approximately1.91. According to another embodiment of the present invention, thesacrificial interface layer 13 may be made of or include a cobalt oxideor a tungsten oxide. The electronegativity of cobalt may beapproximately 1.8, and the electronegativity of tungsten may beapproximately 1.7.

Generally, a work function of a material relates to theelectronegativity of an element or elements making up the material. Forexample, an element having a higher electronegativity has a larger workfunction, and an element having a lower electronegativity has a smallerwork function. In case of a metal, the electronegativity increasesthrough oxidation.

Referring to FIG. 2C, the sacrificial interface layer 13 may be exposedto a reducing atmosphere 14 to reduce the sacrificial interface layer 13and form an initial interface layer 16. The reducing atmosphere 14 mayinclude a hydrogen gas. In an embodiment, the initial interface layer 16may be formed by depositing a sacrificial silicon layer 15 at thehydrogen gas reducing atmosphere.

The sacrificial silicon layer 15 may be deposited under the reducingatmosphere 14 including the hydrogen gas. Since hydrogen has greatreducing power, the sacrificial interface layer 13 may be reduced whenthe sacrificial silicon layer 15 is deposited. A material remaining dueto the reduction of the sacrificial interface layer 13 is qualified asan initial interface layer 16 for short. When the sacrificial interfacelayer 13 is formed of a metal oxide, the metal oxide may be reduced to ametal by hydrogen. For example, when the sacrificial interface layer 13is formed, for example, a nickel oxide (NiO), nickel (Ni) may be formedby a reduction of the nickel oxide (NiO). The initial interface layer 16may have high electronegativity. When the sacrificial silicon layer 15is formed under the reducing atmosphere 14 of hydrogen gas, thesacrificial silicon layer 15 can be deposited at a low temperature. Forexample, the sacrificial silicon layer 15 is formed at a low temperatureof 450° C.

The sacrificial silicon layer 15 may be or include a doped siliconlayer. For example, the sacrificial silicon layer 15 may be a siliconlayer doped with boron. The sacrificial silicon layer 15 may be formedby a CVD method. The sacrificial silicon layer 15 may be deposited usinga hydrogen-containing silicon source gas under the reducing atmosphere14 including the hydrogen gas. According to another embodiment of thepresent invention, the sacrificial silicon layer 15 may be depositedusing the hydrogen-containing silicon source gas and ahydrogen-containing dopant gas under the reducing atmosphere 14including the hydrogen gas. The hydrogen-containing silicon source gasmay include silane (SiH₄) or disilane (Si₂H₆). The hydrogen-containingdopant gas may include boron, borane (BH₃), diborane (B₂H₆) or anycombinations thereof. In this manner, the hydrogen-containing siliconsource gas and the hydrogen-containing dopant gas, which are ascompounds containing hydrogen, may promote the reduction of thesacrificial interface layer 13.

As described above, when the sacrificial silicon layer 15 is formed, thesacrificial interface layer 13 is reduced so that the initial interfacelayer 16 is formed between the sacrificial silicon layer 15 and thedielectric layer 12. The initial interface layer 16 has highelectronegativity and a high work function.

When the sacrificial silicon layer 15 is formed, the dielectric layer 12is be exposed to the silicon source gas, the dopant gas and the reducingatmosphere 14. In other words, the sacrificial interface layer 13 andthe initial interface layer 16 can prevent the dielectric layer 12 frombeing reduced.

Referring to FIG. 2D, a second conductive layer 17 may then be formed onthe sacrificial silicon layer 15. The second conductive layer 17 may beor include a silicon-containing material. For example, the secondconductive layer 17 may be or include a silicon germanium (SiGe) layeror a boron-doped silicon germanium (SiGe) layer. The silicon germanium(SiGe) layer may be deposited using a silicon source gas and a germaniumsource gas. The boron-doped silicon germanium (SiGe) layer may bedeposited using the silicon source gas, the germanium source gas and aboron-containing dopant gas. The silicon germanium (SiGe) layer may usea hydrogen-containing gas such as H₂ as a reaction gas. Each of thesilicon source gas, the germanium source gas and the boron-containingdopant gas may contain hydrogen.

In an embodiment, the second conductive layer 17 may be deposited at atemperature of approximately 400° C. When the second conductive layer 17is deposited at the temperature of approximately 400° C., thesacrificial silicon layer 15 and the initial interface layer 16 mayreact due to a thermal budget. For example, anthe total amount of energytransferred to the sacrificial silicon layer 15 and the initialinterface layer 16 at the elevated temperature (the thermal budget). Aninterface layer 18 may be formed through silicidation. The sacrificialsilicon layer 15 and the initial interface layer 16 may be all consumedduring the silicidation, thereby being completely converted into theinterface layer 18. In other words, the interface layer 18 may be formedthrough full silicidation of the sacrificial silicon layer 15 and theinitial interface layer 16. The interface layer 18 may be referred to asa fully-silicided interface layer (FUSI IL).

The interface layer 18 may include a silicide whose electronegativity ishigh. For example, the interface layer 18 may include a nickel silicide,a cobalt silicide or a tungsten silicide.

Since the interface layer 18 includes a material whose electronegativityis high such as nickel, the interface layer 18 may have a high workfunction of approximately 4.9 eV or higher.

After the second conductive layer 17 is deposited, a thermal process maybe further performed at a temperature of approximately 500° C. or lowerif necessary. Hence, resistance of the interface layer 18 may decrease.

According to another embodiment of the present invention, the secondconductive layer 17 may be formed by stacking a silicon layer and asilicon germanium layer. The silicon layer and the silicon germaniumlayer may be doped with a dopant, for example, boron. For example, aboron-doped silicon layer and a boron-doped silicon germanium layer maybe stacked to form the second conductive layer 17.

As described above, a stack structure of the first conductive layer 11,the dielectric layer 12, the interface layer 18 and the secondconductive layer 17 that are formed through a series of processes maybecome a capacitor. The first conductive layer 11 may be qualified as abottom electrode of the capacitor or a storage node, and the secondconductive layer 17 may be qualified as a top electrode of the capacitoror a plate. The interface layer 18 and the dielectric layer 12 may be indirect contact. The interface layer 18 and the second conductive layer17 may be in direct contact. Since the second conductive layer 17includes the silicon germanium layer, the top electrode of the capacitormay be formed of a non-metal material or a non-metal nitride.

FIGS. 3A to 3C are cross-sectional views illustrating another example ofa method for fabricating a semiconductor device in accordance with anembodiment of the present invention illustrated in FIG. 1A. Detaileddescriptions of the processes which are identical to those describedabove with reference to FIGS. 2A to 2D are omitted.

Referring to FIG. 3A, a method for fabricating the semiconductor devicein accordance with a modified example of an embodiment of the presentinvention may include forming a sacrificial interface layer 13′ on adielectric layer 12 after forming the dielectric layer 12 through theprocesses described above with reference to FIGS. 2A and 2B. Thesacrificial interface layer 13′ may include an oxide of aneasily-reduced material. The sacrificial interface layer 13′ may includean oxide whose electronegativity is high. The sacrificial interfacelayer 13′ may include an easily-reduced oxide whose electronegativity ishigh.

For example in an embodiment, the sacrificial interface layer 13′ may bemade of or include an easily-reduced, high electronegativity oxide suchas an oxide of nickel, i.e., a nickel oxide (NiO). According to anotherembodiment of the present invention, the sacrificial interface layer 13′may be made of or include a cobalt oxide or a tungsten oxide. Thesacrificial interface layer 13′ may have a fourth thickness D11.

The fourth thickness D11 of the sacrificial interface layer 13′ shown inFIG. 3A may be larger than a first thickness D1 of the sacrificialinterface layer 13 shown in FIG. 2B. The thickness of the sacrificialinterface layer 13′ may be approximately 2 nm or less.

Referring to FIG. 3B, a sacrificial silicon layer 15 may be formed undera hydrogen gas atmosphere 14. When the sacrificial silicon layer 15 isdeposited, an initial interface layer 16′ may be formed by a reductionof the sacrificial interface layer 13′. The initial interface layer 16′may be formed between the sacrificial silicon layer 15 and thedielectric layer 12 and may have a fifth thickness D12. The fifththickness D12 of the initial interface layer 16′ may be formed to belarger than a second thickness D2 of the initial interface layer 16shown in FIG. 2C. The initial interface layer 16′ may have the samethickness (D11=D12) as the sacrificial interface layer 13′.

Referring to FIG. 3C, a second conductive layer 17′ may be formed on thesacrificial silicon layer 15. The second conductive layer 17′ may be orinclude a silicon-containing material. The second conductive layer 17′may be or include a silicon germanium (SiGe) layer or a boron-dopedsilicon germanium (SiGe) layer. The silicon germanium (SiGe) layer maybe deposited using a silicon source gas and a germanium source gas. Theboron-doped silicon germanium (SiGe) layer may be deposited using thesilicon source gas, the germanium source gas and a boron-containingdopant gas. The silicon germanium (SiGe) layer may use ahydrogen-containing gas such as H₂ as a reaction gas. Each of thesilicon source gas, the germanium source gas and the boron-containingdopant gas may contain hydrogen.

The second conductive layer 17′ may be deposited at a temperature ofapproximately 400° C. When the second conductive layer 17′ is depositedat the temperature of approximately 400° C., the sacrificial siliconlayer 15 and the initial interface layer 16′ react due to the thermalbudget. For example, an interface layer 18′ may be formed throughsilicidation. The sacrificial silicon layer 15 and the initial interfacelayer 16′ may be all consumed during the silicidation, thereby beingcompletely converted into the interface layer 18′. In other words, theinterface layer 18′ may be formed through full silicidation of thesacrificial silicon layer 15 and the initial interface layer 16′. Theinterface layer 18′ may have a sixth thickness D13.

The sixth thickness D13 of the interface layer 18′ shown in FIG. 3C maybe larger than a third thickness D3 of the interface layer 18 shown inFIG. 2D.

The interface layer 18′ may be formed of a metal-rich metal silicide(M_(x)Si_(y)). The metal-rich metal silicide (M_(x)Si_(y)) may have aratio of metal to silicon (x/y) greater than 1. The interface layer 18′may include a nickel-rich nickel silicide. For example, the nickel-richnickel silicide may include a Ni₂Si phase or a Ni₃Si₂ phase. Theinterface layer 18′ may include a cobalt-rich cobalt silicide or atungsten-rich tungsten silicide.

Since the interface layer 18′ includes a material whoseelectronegativity is high such as nickel, the interface layer 18′ mayhave a high work function of approximately 4.9 eV or higher. Besides,since the interface layer 18′ includes the metal-rich metal silicide,the interface layer 18′ may have a greatly higher work function. Forexample, a nickel silicide having the Ni₂Si phase may have the workfunction ranging from approximately 4.9 eV to approximately 5.0 eV. Thenickel silicide having the Ni₂Si phase may have a higher work functionthan a nickel silicide having a NiSi phase.

As described above, the interface layer 18′ may be formed of themetal-rich metal silicide having a large metal content. The metalcontent may be adjusted by increasing the thickness of the sacrificialinterface layer 13′ and increasing the amount of hydrogen gasimplantation when the second conductive layer 17′ is deposited.

A series of processes for forming the interface layer 18′ may berepresented by the following chemical formula:

NiO+H*+Si₂H₆*→Ni_(x)Si_(y)(x>y, x≥2)

According to the embodiments described above, a leakage current may beimproved without deterioration of the equivalent oxide layer thickness,and interface resistance may be also improved. In addition, the processcost may decrease while simplifying the process because a TiN process isnot performed on the second conductive layers 17 and 17′.

As a comparative example, an upper portion of the dielectric layer 12may be directly deposited with a titanium nitride (TiN). A TiNdeposition process may be performed by using TiCl₄ and NH₃.Subsequently, a silicon germanium layer may be deposited on the TiN. Adeposition process of the silicon germanium layer may be performed byusing a gas such as SiH₄ and GeH₄.

NH₃, SiH₄ and GeH₄ used during such a SiGe/TiN stack deposition processmay lead to a reduction of the dielectric layer 12 as strong reductants.Due to the reduction of the dielectric layer 12, the loss of oxygen mayoccur in the dielectric layer 12 and the quality of the layer maydeteriorate.

According to an embodiment and the modified example of the presentinvention, since the sacrificial interface layers 13 and 13′ which areeasily reduced are formed on the dielectric layer 12, the reduction ofthe dielectric layer 12 may not occur although the dielectric layer 12is exposed to a series of processes including a subsequent hydrogen gas.Accordingly, oxygen of the dielectric layer 12 may be prevented frombeing lost.

The use of the top electrode having a high work function to decrease theleakage current of the capacitor does not deteriorate the equivalentoxide layer thickness of the dielectric layer. TiN is widely known tothose skilled in the art as the top electrode having high work function.The high work function of TiN is approximately 4.9 eV.

Recently, in order to decrease greatly the leakage current, a topelectrode having a high work function of approximately 4.9 eV or higherhas been required. It is known that such materials as Ru, Pt, etc. havea higher work function than TiN. However, since these noble metals areexpensive and an etch process thereof is difficult, there is limitationin applying them to high integrated capacitors.

According to the present invention, as the interface layers 18 and 18′are formed by using materials whose electronegativity is high, thedesired high work function of approximately 4.9 eV or higher can beobtained, thereby improving the leakage current of a capacitor withoutdeterioration of the equivalent oxide layer thickness.

FIGS. 4A to 4C are cross-sectional views illustrating yet anotherexample of method for fabricating the semiconductor device in accordancewith an embodiment of the present invention. Detailed descriptions ofthe processes which overlap with those described above with reference toFIGS. 2A to 2D are omitted.

Referring to FIG. 4A, a method for fabricating the semiconductor devicein accordance with an embodiment of the present invention may includeforming a sacrificial interface layer 13 on a dielectric layer 12 afterforming the dielectric layer 12 through the processes described abovewith reference to FIGS. 2A and 2B. The sacrificial interface layer 13may be made of or include a nickel oxide (NiO). According to anotherembodiment of the present invention, the sacrificial interface layer 13may be made of or include a cobalt oxide or a tungsten oxide. Thesacrificial interface layer 13 may be formed by an Atomic LayerDeposition (ALD) or any other suitable method.

Subsequently, an auxiliary sacrificial interface layer 21 may be formedon the sacrificial interface layer 13. The auxiliary sacrificialinterface layer 21 may be formed, for example, by the ALD. The auxiliarysacrificial interface layer 21 may be or include a silicon-containingmaterial. The auxiliary sacrificial interface layer 21 may include asilicon oxide (SiO₂).

The sacrificial interface layer 13 and the auxiliary sacrificialinterface layer 21 may be formed, for example, by the ALD. Thesacrificial interface layer 13 and the auxiliary sacrificial interfacelayer 21 may be formed in a bi-layer structure. For example, thesacrificial interface layer 13 and the auxiliary sacrificial interfacelayer 21 may be formed in the bi-layer structure of SiO₂/NiO.

According to another embodiment of the present invention, thesacrificial interface layer 13 and the auxiliary sacrificial interfacelayer 21 may be formed in a laminate structure. For example, thelaminate structure may include alternating layers of the sacrificialinterface layer 13 and the auxiliary sacrificial interface layer 21.

FIG. 5 is a cross-sectional view illustrating a laminate structure of anickel oxide and a silicon oxide.

Referring to FIG. 5, the nickel oxide and the silicon oxide may bealternately deposited to form the laminate structure such asSiO₂/NiO/SiO₂/NiO. Each of the nickel oxide and the silicon oxide may bealternately deposited at least twice.

Total thickness of the sacrificial interface layer 13 and the auxiliarysacrificial interface layer 21 may be 2 nm or less.

Referring to FIG. 4B, the sacrificial interface layer 13 and theauxiliary sacrificial interface layer 21 may be exposed to a reducingatmosphere 14. When the sacrificial interface layer 13 and the auxiliarysacrificial interface layer 21 are exposed to the reducing atmosphere14, the sacrificial interface layer 13 and the auxiliary sacrificialinterface layer 21 may be reduced. An initial interface layer 16 may beformed by such a reduction of the sacrificial interface layer 13.Besides, an auxiliary initial interface layer 21′ may be formed by sucha reduction of the auxiliary sacrificial interface layer 21.

According to an embodiment of the present invention, a depositionprocess of a sacrificial silicon layer 15 may be performed to form theinitial interface layer 16. The deposition process of the sacrificialsilicon layer 15 may be performed under the reducing atmosphere 14including a hydrogen gas.

The sacrificial silicon layer 15 may be deposited under the reducingatmosphere 14 including a large amount of the hydrogen gas. Sincehydrogen has great reducing power, the sacrificial interface layer 13and the auxiliary sacrificial interface layer 21 may be reduced when thesacrificial silicon layer 15 is deposited. A material remaining due tothe reduction of the sacrificial interface layer 13 is qualified as theinitial interface layer 16 for short. When the sacrificial interfacelayer 13 is formed of a metal oxide, the metal oxide may be reduced to ametal by hydrogen. For example, when the sacrificial interface layer 13is formed, for example, a nickel oxide (NiO), nickel (Ni) may be formedby a reduction of the nickel oxide (NiO). The initial interface layer 16may have high electronegativity. When the sacrificial silicon layer 15is formed under the reducing atmosphere 14, the sacrificial siliconlayer 15 may be deposited at a low temperature. A material remaining dueto the reduction of the auxiliary sacrificial interface layer 21 isqualified as the auxiliary initial interface layer 21′ for short. Whenthe auxiliary sacrificial interface layer 21 is formed of a siliconoxide, the silicon oxide may be converted into silicon by hydrogen. Forexample, the auxiliary initial interface layer 21′ may be a siliconlayer.

The sacrificial silicon layer 15 may be or include a doped siliconlayer. The sacrificial silicon layer 15 may be a silicon layer dopedwith boron. The sacrificial silicon layer 15 may be formed, for example,CVD or any other suitable method. The sacrificial silicon layer 15 maybe deposited using a hydrogen-containing silicon source gas under thereducing atmosphere 14 including the hydrogen gas. According to anotherembodiment of the present invention, the sacrificial silicon layer 15may be deposited using the hydrogen-containing silicon source gas and ahydrogen-containing dopant gas under the reducing atmosphere 14including the hydrogen gas. The hydrogen-containing silicon source gasmay include silane (SiH₄) or disilane (Si₂H₆). The hydrogen-containingdopant gas may include boron, borane (BH₃), diborane (B₂H₆) or anycombinations thereof. In this manner, the hydrogen-containing siliconsource gas and the hydrogen-containing dopant gas, which are compoundscontaining hydrogen, may promote the reduction of the sacrificialinterface layer 13.

As described above, when the sacrificial silicon layer 15 is formed, thesacrificial interface layer 13 may be reduced so that the initialinterface layer 16 may be formed between the sacrificial silicon layer15 and the dielectric layer 12. The initial interface layer 16 has highelectronegativity and high work function.

When the sacrificial silicon layer 15 is formed, the dielectric layer 12is not exposed to the hydrogen-containing silicon source gas, thehydrogen-containing dopant gas and the reducing atmosphere 14. In otherwords, the sacrificial interface layer 13 and the initial interfacelayer 16 prevent the dielectric layer 12 from being reduced.

Referring to FIG. 4C, a second conductive layer 17 may be formed on thesacrificial silicon layer 15. The second conductive layer 17 may be madeof or include a silicon-containing material. The second conductive layer17 may be made of or include a silicon germanium (SiGe) layer or aboron-doped silicon germanium (SiGe) layer. The silicon germanium (SiGe)layer may be deposited using a silicon source gas and a germanium sourcegas. The boron-doped silicon germanium (SiGe) layer may be depositedusing the silicon source gas, the germanium source gas and aboron-containing dopant gas. The silicon germanium (SiGe) layer may usea hydrogen-containing gas such as H₂ as a reaction gas. Each of thesilicon source gas, the germanium source gas and the boron-containingdopant gas may contain hydrogen.

The second conductive layer 17 may be deposited at a temperature ofapproximately 400° C. When the second conductive layer 17 is depositedat the temperature of approximately 400° C., the sacrificial siliconlayer 15, the auxiliary initial interface layer 21′ and the initialinterface layer 16 react due to the thermal budget. For example, aninterface layer 18″ may be formed through silicidation. The sacrificialsilicon layer 15, the auxiliary initial interface layer 21′ and theinitial interface layer 16 may be all consumed during the silicidation,thereby being completely converted into the interface layer 18″. Inother words, the interface layer 18″ may be formed through fullysilicidation of the sacrificial silicon layer 15, the auxiliary initialinterface layer 21′ and the initial interface layer 16. The interfacelayer 18″ may be referred to as a fully-silicided interface layer (FUSIIL).

The interface layer 18″ may include a silicide whose electronegativityis high. For example, the interface layer 18″ may include a nickelsilicide, a cobalt silicide or a tungsten silicide.

Since the interface layer 18″ includes a material whoseelectronegativity is high such as nickel, the interface layer 18″ mayhave a high work function. The interface layer 18″ may have the highwork function of approximately 4.9 eV or higher.

As described above, the interface layer 18″ may be formed through thesilicidation of the sacrificial silicon layer 15, the auxiliary initialinterface layer 21′ and the initial interface layer 16. As the auxiliaryinitial interface layer 21′ is additionally formed, the interface layer18″ may be easily controlled to be formed.

After the second conductive layer 17 is deposited, a thermal process maybe further performed at a temperature of approximately 500° C. or lowerif necessary. Hence, resistance of the interface layer 18″ may decrease.

According to another embodiment of the present invention, the secondconductive layer 17 may be formed by stacking a silicon layer and asilicon germanium layer. The silicon layer and the silicon germaniumlayer may be doped with a dopant, for example, boron. For example, aboron-doped silicon layer and a boron-doped silicon germanium layer maybe stacked to form the second conductive layer 17.

As described above, a stack structure of a first conductive layer 11,the dielectric layer 12, the interface layer 18″ and the secondconductive layer 17 that are formed through a series of processes maybecome a capacitor.

FIG. 6A is a cross-sectional view of a semiconductor device 200 inaccordance with an embodiment of the present invention. Detaileddescriptions of the components and configurations of the semiconductordevice which overlap with those shown as above with reference to FIG. 1Aare omitted.

Referring to FIG. 6A, the semiconductor device 200 may include a firstconductive layer 101, a dielectric layer 102, and a second conductivelayer 103. An interface layer 204 may be formed between the dielectriclayer 102 and the second conductive layer 103.

The interface layer 204 may include a conductive material. The interfacelayer 204 may be or include a high work function material. The interfacelayer 204 may be or include the high work function material ofapproximately 4.9 eV or higher. The interface layer 204 may be orinclude a germanide material whose electronegativity is high. Theinterface layer 204 may be or include a metal germanide. The interfacelayer 204 may be or include a nickel germanide, a cobalt germanide or atungsten germanide. The nickel germanide may have a high work functionof approximately 5.2 eV.

FIG. 6B is a cross-sectional view of a capacitor as an applicationexample of the semiconductor device in accordance with an embodiment ofthe present invention.

Referring to FIG. 6B, a capacitor 200M may include a bottom electrode101M, a dielectric layer 102M, an interface layer 204M, and a topelectrode 103M.

The bottom electrode 101M may be formed of a metal nitride. The bottomelectrode 101M may be formed, for example, of a titanium nitride (TiN).

The top electrode 103M may be formed, for example, of a silicongermanium (SiGe) layer. The silicon germanium layer may be doped with adopant, for example, boron.

The dielectric layer 102M may have a ZAZ (ZrO₂/Al₂O₃/ZrO₂) stackstructure. The dielectric layer 102M may include a first zirconium oxide102A, an aluminum oxide 102B and a second zirconium oxide 102C which aresequentially stacked. The dielectric layer 102M may further include analuminum oxide 102D formed on the second zirconium oxide 102C. Thisstructure is referred to as a ZAZA stack structure.

The interface layer 204M may be formed, for example, a nickel germanide(Ni-Germanide).

FIGS. 7A and 7B are cross-sectional views illustrating an example of amethod for fabricating the semiconductor device in accordance with thesecond embodiment of the present invention. Detailed descriptions of theprocesses which overlap with those shown above with reference to FIGS.2A to 2D are omitted.

The method for fabricating the semiconductor device in accordance withan embodiment of the present invention may include forming a sacrificialinterface layer 13 on a dielectric layer 12 after forming the dielectriclayer 12 through the processes described above with reference to FIGS.2A and 2B. The sacrificial interface layer 13 may be made of or includea nickel oxide (NiO). According to another embodiment of the presentinvention, the sacrificial interface layer 13 may be made of or includea cobalt oxide or a tungsten oxide. The sacrificial interface layer 13may be formed by an Atomic Layer Deposition (ALD) or any other suitablemethod.

Referring now to FIG. 7A, after the sacrificial interface layer 13 isformed, the sacrificial interface layer 13 may be exposed to a reducingatmosphere 14. When the sacrificial interface layer 13 is exposed to thereducing atmosphere 14, the sacrificial interface layer 13 may bereduced. An initial interface layer 16 may be formed by such a reductionof the sacrificial interface layer 13.

According to the illustrated embodiment of the present invention, adeposition process of a sacrificial germanium layer 31 may be performedto form the initial interface layer 16. The deposition process of thesacrificial germanium layer 31 may be performed under a reducingatmosphere 14 including a hydrogen gas.

Since hydrogen has great reducing power, the sacrificial interface layer13 may be reduced when the sacrificial germanium layer 31 is deposited.A material remaining due to the reduction of the sacrificial interfacelayer 13 is qualified as the initial interface layer 16 for short. Whenthe sacrificial interface layer 13 is formed of a metal oxide, the metaloxide may be reduced to a metal by hydrogen. For example, when thesacrificial interface layer 13 is formed, for example, of a nickel oxide(NiO), nickel (Ni) may be formed by a reduction of the nickel oxide(NiO). The initial interface layer 16 may have high electronegativity.When the sacrificial germanium layer 31 is formed under the reducingatmosphere 14 including a great amount of the hydrogen gas, thesacrificial germanium layer 31 may be deposited at a low temperature.

The sacrificial germanium layer 31 may have a doped germanium layer. Thesacrificial germanium layer 31 may be a germanium layer doped withboron. The sacrificial germanium layer 31 may be formed, for example, byChemical Vapor Deposition (CVD) or any other suitable method. Thesacrificial germanium layer 31 may be deposited using ahydrogen-containing germanium source gas under the reducing atmosphere14 including the hydrogen gas. According to another embodiment of thepresent invention, the sacrificial germanium layer 31 may be depositedusing the hydrogen-containing germanium source gas and ahydrogen-containing dopant gas under the reducing atmosphere 14including the hydrogen gas. In an embodiment, a compound gas containinghydrogen such as GeH₄ may be used as the hydrogen-containing germaniumsource gas. The hydrogen-containing dopant gas may include boron, borane(BH₃), diborane (B₂H₆) or any combinations thereof. In this manner, thehydrogen-containing germanium source gas and the hydrogen-containingdopant gas, which are as compounds containing hydrogen, may promote thereduction of the sacrificial interface layer 13.

As described above, when the sacrificial germanium layer 31 is formed,the sacrificial interface layer 13 may be reduced so that the initialinterface layer 16 may be formed between the sacrificial germanium layer31 and the dielectric layer 12. The initial interface layer 16 has highelectronegativity and high work function.

When the sacrificial germanium layer 31 is formed, the dielectric layer12 is not exposed to the hydrogen-containing germanium source gas, thehydrogen-containing dopant gas and the reducing atmosphere 14. In otherwords, the sacrificial interface layer 13 and the initial interfacelayer 16 prevent the dielectric layer 12 from being reduced.

Referring to FIG. 7B, a second conductive layer 17 may be formed on thesacrificial germanium layer 31. The second conductive layer 17 may be orinclude a silicon-containing material. The second conductive layer 17may be or include a silicon germanium (SiGe) layer or a boron-dopedsilicon germanium (SiGe) layer. The silicon germanium (SiGe) layer maybe deposited using a silicon source gas and a germanium source gas. Theboron-doped silicon germanium (SiGe) layer may be deposited using thesilicon source gas, the germanium source gas and a boron-containingdopant gas. The silicon germanium (SiGe) layer may use ahydrogen-containing gas such as H₂ as a reaction gas. Each of thesilicon source gas, the germanium source gas and the boron-containingdopant gas may contain hydrogen.

The second conductive layer 17 may be deposited at a temperature ofapproximately 400° C. When the second conductive layer 17 is depositedat the temperature of approximately 400° C., the sacrificial germaniumlayer 31 and the initial interface layer 16 react due to the thermalbudget. For example, an interface layer 32 may be formed through agermanide reaction. The sacrificial germanium layer 31 and the initialinterface layer 16 may be all consumed during the germanide reaction,thereby being completely converted into the interface layer 32. In otherwords, the interface layer 32 may be formed through full-germanidereaction of the sacrificial germanium layer 31 and the initial interfacelayer 16. The interface layer 32 may be referred to as a fully-germanideinterface layer (FUGE IL). The interface layer 32 may be or include ametal germanide.

The interface layer 32 may be or include a germanide whoseelectronegativity is high. For example, the interface layer 32 may be orinclude a nickel germanide, a cobalt germanide or a tungsten germanide.

Since the interface layer 32 includes a material whose electronegativityis high such as nickel, the interface layer 32 may have a high workfunction of approximately 4.9 eV or higher. For example, a nickelgermanide (NiGe) may have a high work function of approximately 5.2 eV.The nickel germanide (NiGe) may have a higher work function than thenickel silicide.

After the second conductive layer 17 is deposited, a thermal process maybe further performed at a temperature of approximately 500° C. or lowerif necessary. Hence, resistance of the interface layer 32 may decrease.

According to another embodiment of the present invention, the secondconductive layer 17 may be formed by stacking a silicon layer and asilicon germanium layer. The silicon layer and the silicon germaniumlayer may be doped with a dopant, for example, boron. For example, aboron-doped silicon (Si) layer and a boron-doped silicon germanium(SiGe) layer may be stacked to form the second conductive layer 17.

As described above, a stack structure of a first conductive layer 11,the dielectric layer 12, the interface layer 32 and the secondconductive layer 17 that are formed through a series of processes maybecome a capacitor.

FIGS. 8A to 8C are cross-sectional views illustrating another example ofthe method for fabricating the semiconductor device in accordance withan embodiment of the present invention.

The method for fabricating the semiconductor device in accordance withan embodiment of the present invention may include forming a sacrificialinterface layer 13 on a dielectric layer 12 after forming the dielectriclayer 12 through the processes described above with reference to FIGS.2A and 2B. The sacrificial interface layer 13 may be made of or includea nickel oxide (NiO). According to another embodiment of the presentinvention, the sacrificial interface layer 13 may be made of or includea cobalt oxide or a tungsten oxide. The sacrificial interface layer 13may be formed by an Atomic Layer Deposition (ALD) or any other suitablemethod.

Subsequently, referring to FIG. 8A, an auxiliary sacrificial interfacelayer 41 may be formed on the sacrificial interface layer 13. Theauxiliary sacrificial interface layer 41 may be formed, for example, byALD or any other suitable method. The auxiliary sacrificial interfacelayer 41 may include a germanium-containing material. The auxiliarysacrificial interface layer 41 may include a germanium oxide (GeO₂).

The sacrificial interface layer 13 and the auxiliary sacrificialinterface layer 41 may be formed, for example, by ALD. The sacrificialinterface layer 13 and the auxiliary sacrificial interface layer 41 maybe formed in a bi-layer structure. For example, the sacrificialinterface layer 13 and the auxiliary sacrificial interface layer 41 maybe formed in the bi-layer structure of GeO₂/NiO.

According to another embodiment of the present invention, thesacrificial interface layer 13 and the auxiliary sacrificial interfacelayer 41 may be formed in a laminate structure.

FIG. 9 is a cross-sectional view illustrating a laminate structure of anickel oxide and a germanium oxide.

Referring to FIG. 9, the nickel oxide and the germanium oxide may bealternately deposited to form the laminate structure such asGeO₂/NiO/GeO₂/NiO. Each of the nickel oxide and the germanium oxide maybe alternately deposited at least twice.

Total thickness of the sacrificial interface layer 13 and the auxiliarysacrificial interface layer 41 may be 2 nm or less.

Referring to FIG. 8B, the sacrificial interface layer 13 and theauxiliary sacrificial interface layer 41 may be exposed to the reducingatmosphere 14. When the sacrificial interface layer 13 and the auxiliarysacrificial interface layer 41 are exposed to the reducing atmosphere14, the sacrificial interface layer 13 and the auxiliary sacrificialinterface layer 41 may be reduced. An initial interface layer 16 may beformed by such a reduction of the sacrificial interface layer 13.Besides, an auxiliary initial interface layer 41′ may be formed by sucha reduction of the auxiliary sacrificial interface layer 41.

According to an embodiment of the present invention, a depositionprocess of a sacrificial germanium layer 31 may be performed to form theinitial interface layer 16. The deposition process of the sacrificialgermanium layer 31 may be performed under the reducing atmosphere 14including a hydrogen gas.

The sacrificial germanium layer 31 may be deposited under the reducingatmosphere 14 including a large amount of the hydrogen gas. Sincehydrogen has great reducing power, the sacrificial interface layer 13and the auxiliary sacrificial interface layer 41 may be reduced when thesacrificial germanium layer 31 is deposited. A material remaining due tothe reduction of the sacrificial interface layer 13 is qualified as theinitial interface layer 16 for short. When the sacrificial interfacelayer 13 is formed of a metal oxide, the metal oxide may be reduced to ametal by hydrogen. For example, when the sacrificial interface layer 13is formed, for example, a nickel oxide (NiO), nickel (Ni) may be formedby a reduction of the nickel oxide (NiO). The initial interface layer 16may have high electronegativity. When the sacrificial germanium layer 31is formed under the reducing atmosphere 14, the sacrificial germaniumlayer 31 may be deposited at a low temperature. A material remaining dueto the reduction of the auxiliary sacrificial interface layer 41 isqualified as the auxiliary initial interface layer 41′ for short. Whenthe auxiliary sacrificial interface layer 41 is formed of a germaniumoxide, the germanium oxide may be converted into germanium by hydrogen.For example, the auxiliary initial interface layer 41′ may be agermanium layer.

The sacrificial germanium layer 31 may include a doped germanium layer.The sacrificial germanium layer 31 may be a germanium layer doped withboron. The sacrificial germanium layer 31 may be formed, for example, byChemical Vapor Deposition (CVD) or any other suitable method. Thesacrificial germanium layer 31 may be formed using a hydrogen-containinggermanium source gas and a hydrogen-containing dopant gas. Thehydrogen-containing germanium source gas may include GeH₄. Thehydrogen-containing dopant gas may include borane (BH₃), diborane (B₂H₆)or any combinations thereof. In this manner, the hydrogen-containinggermanium source gas and the hydrogen-containing dopant gas, which areas compounds containing hydrogen, may promote the reduction of thesacrificial interface layer 13.

As described above, when the sacrificial germanium layer 31 is formed,the sacrificial interface layer 13 may be reduced so that the initialinterface layer 16 may be formed between the sacrificial germanium layer31 and the dielectric layer 12. The initial interface layer 16 has highelectronegativity and high work function.

When the sacrificial germanium layer 31 is formed, the dielectric layer12 is not exposed to the hydrogen-containing germanium source gas, thehydrogen-containing dopant gas and the reducing atmosphere 14. In otherwords, the sacrificial interface layer 13 and the initial interfacelayer 16 prevent the dielectric layer 12 from being reduced.

Referring to FIG. 8C, a second conductive layer 17 may be formed on thesacrificial germanium layer 31. The second conductive layer 17 may be orinclude a silicon-containing material. The second conductive layer 17may be or include a silicon germanium (SiGe) layer or a boron-dopedsilicon germanium (SiGe) layer. The silicon germanium (SiGe) layer maybe deposited using a silicon source gas and a germanium source gas. Theboron-doped silicon germanium (SiGe) layer may be deposited using thesilicon source gas, the germanium source gas and a boron source gas. Thesilicon germanium (SiGe) layer may use a hydrogen-containing gas such asH₂ as a reaction gas.

The second conductive layer 17 may be deposited at an elevatedtemperature, for example a temperature of approximately 400° C. When thesecond conductive layer 17 is deposited at the temperature ofapproximately 400° C., the sacrificial germanium layer 31, the auxiliaryinitial interface layer 41′ and the initial interface layer 16 react dueto the thermal budget. For example, an interface layer 32′ may be formedthrough a germanide reaction. The sacrificial germanium layer 31, theauxiliary initial interface layer 41′ and the initial interface layer 16may be all consumed during the germanide reaction, thereby beingcompletely converted into the interface layer 32′. In other words, theinterface layer 32′ may be formed through a fully-germanide reaction ofthe sacrificial germanium layer 31, the auxiliary initial interfacelayer 41′ and the initial interface layer 16. The interface layer 32′may be referred to as a fully-germanide interface layer (FUGE IL).

The interface layer 32′ may be or include a germanide of a materialwhose electronegativity is high. For example, the interface layer 32′may be or include a nickel germanide, a cobalt germanide or a tungstengermanide.

Since the interface layer 32′ includes a material whoseelectronegativity is high such as nickel, the interface layer 32′ mayhave a high work function. The interface layer 32′ may have the highwork function of approximately 4.9 eV or higher. For example, a nickelgermanide (NiGe) may have a high work function of approximately 5.2 eV.The nickel germanide (NiGe) may have a higher work function than thenickel silicide.

After the second conductive layer 17 is deposited, a thermal process maybe further performed at a temperature of approximately 500° C. or lowerif necessary. Hence, resistance of the interface layer 32′ may decrease.

According to another embodiment of the present invention, the secondconductive layer 17 may be formed by sequentially stacking a siliconlayer and a silicon germanium layer. The silicon layer and the silicongermanium layer may be doped with a dopant, for example, boron. Forexample, a boron-doped silicon (Si) layer and a boron-doped silicongermanium (SiGe) layer may be stacked to form the second conductivelayer 17.

As described above, a stack structure of a first conductive layer 11,the dielectric layer 12, the interface layer 32′ and the secondconductive layer 17 that are formed through a series of processes maybecome a capacitor.

FIGS. 10A to 10E are cross-sectional views illustrating a method forfabricating a DRAM capacitor in accordance with embodiments of thepresent invention. A sacrificial interface layer, a sacrificial layer,an initial interface layer, an interface layer, etc. shown in FIGS. 10Ato 10E refer to the aforementioned embodiments of the present invention.

Referring to FIG. 10A, an inter-layer dielectric layer 52 may be formedon a semiconductor substrate 51. A storage node contact plug 53 coupledto a portion of the semiconductor substrate 51 may be formed topenetrate through the inter-layer dielectric layer 52. The storage nodecontact plug 53 may be formed of any suitable material including apolysilicon, a metal, a metal nitride, or combinations thereof. Althoughnot illustrated, a cell transistor and a bit line may be further formedbefore the inter-layer dielectric layer 52 is formed. The celltransistor may include a buried word line structure.

A bottom electrode 54 may be formed on the storage node contact plug 53.The bottom electrode 54 may, for example, have a cylindrical shape.According to another embodiment of the present invention, the bottomelectrode 54 may have a pillar shape. In an embodiment, the bottomelectrode 54 may be formed of a metal nitride, such as, for example, atitanium nitride.

The bottom electrode 54 may be supported by first and second supporters55A and 55B. The first supporter 55A may be coupled to a bottom portionof the bottom electrode 54. The second supporter 55B may be coupled to atop portion of the bottom electrode 54. The first and second supporters55A and 55B may include a silicon nitride, a silicon carbide, or acombination thereof. The first supporter 55A may also be an etch stoplayer.

Referring to FIG. 10B, a dielectric layer 56 may be formed. Thedielectric layer 56 may have a ZAZA stack structure. The dielectriclayer 56 may cover the bottom electrode 54 and the first and secondsupporters 55A and 55B.

Referring to FIG. 10C, a sacrificial interface layer 57 may be formed onthe dielectric layer 56. The sacrificial interface layer 57 may beformed, for example, a nickel oxide. According to another embodiment ofthe present invention, the sacrificial interface layer 57 may be formedof a cobalt oxide or a tungsten oxide.

Referring to FIG. 10D, a sacrificial layer 59 may be formed at areducing atmosphere 58. The reducing atmosphere 58 may contain ahydrogen gas. The sacrificial layer 59 may include a silicon layer or agermanium layer. In an embodiment, the sacrificial layer 59 may bedeposited using a compound gas containing hydrogen.

As the sacrificial layer 59 is formed under the reducing atmosphere 58,an initial interface layer 57′ may be formed by such a reduction of thesacrificial interface layer 57. For example, the sacrificial interfacelayer 57 may be or include a nickel oxide, and the initial interfacelayer 57′ may be or include nickel. In other words, the nickel mayremain due to a reduction of the nickel oxide.

Referring to FIG. 10E, a top electrode 60 may be formed. The topelectrode 60 may be or include a silicon germanium layer. When the topelectrode 60 is formed, the sacrificial layer 59 and the initialinterface layer 57′ react due to the thermal budget. For example, aninterface layer 61 may be formed through silicidation or a germanidereaction. The interface layer 61 may be a metal silicide or a metalgermanide. The interface layer 61 may be a nickel silicide or a nickelgermanide.

According to another embodiment of the present invention, the interfacelayer 61 of the DRAM capacitor may be formed of a metal-rich metalsilicide.

According to another embodiment of the present invention, a method forforming the interface layer 61 of the DRAM capacitor may use a stack ofa sacrificial interface layer and an auxiliary sacrificial interfacelayer. For example, the method for fabricating the DRAM capacitor mayinclude the processes described above with reference to FIGS. 4A to 4C.Besides, the method for fabricating the DRAM capacitor may include theprocesses described above with reference to FIGS. 8A to 8C.

FIG. 11 is a cross-sectional view of the DRAM capacitor in accordancewith embodiments of the present invention.

Referring to FIG. 11, a pillar-type bottom electrode 54′, a dielectriclayer 56′, an interface layer 61′ and a top electrode 60′ may be formed.The DRAM capacitor shown in FIG. 11 may be fabricated by the methoddescribed above with reference to FIGS. 10A to 10E. However, we notethat the pillar-type bottom electrode 54′ may be formed by a method thatis different from the method for forming the bottom electrode 54 shownin FIG. 10A.

According to the embodiments of the present invention, the interfacelayer may be formed between the dielectric layer and the top electrodeusing a material having a high electronegativity, whereby the leakagecurrent may be greatly reduced. Thus, refresh characteristics of theDRAM may be improved.

According to the embodiments of the present invention, since theequivalent oxide layer thickness and capacitance are not affected, asensing margin of the DRAM may be maintained and the reliability of theDRAM may be improved.

According to various embodiments of the present invention, an interfacelayer having a high work function while suppressing the reduction of adielectric layer may be formed.

Also, according to various embodiments of the present invention, aninterface layer may be formed between a dielectric layer and a topelectrode using a material having a high electronegativity, whereby theleakage current of a capacitor may be reduced.

Finally, according to various embodiments of the present invention, adielectric layer may be prevented from being reduced from a topelectrode, whereby the capacitance and the leakage current may beimproved.

While the present invention has been described with respect to thespecific embodiments, it should be noted that the embodiments are fordescribing, not limiting, the present invention. Further, it should benoted that the present invention may be achieved in various ways throughsubstitution, change, and modification, by those skilled in the artwithout departing from the scope of the present invention as defined bythe following claims.

What is claimed is:
 1. A capacitor, comprising: a bottom electrode; adielectric layer formed on the bottom electrode; a high work functioninterface layer formed on the dielectric layer; and a top electrodeformed on the high work function interface layer, wherein the high workfunction interface layer includes a silicide having a highelectronegativity.
 2. The capacitor of claim 1, wherein the high workfunction interface layer includes a metal silicide or a metal-rich metalsilicide.
 3. The capacitor of claim 1, wherein the high work functioninterface layer includes a nickel silicide or a nickel-rich nickelsilicide.
 4. The capacitor of claim 1, wherein the high work functioninterface layer includes a cobalt silicide, a cobalt-rich cobaltsilicide, a tungsten silicide, or a tungsten-rich tungsten silicide. 5.The capacitor of claim 1, herein the top electrode includes a silicongermanium layer.
 6. The capacitor of claim 1, wherein the top electrodeincludes a boron-doped silicon germanium layer.
 7. The capacitor ofclaim 1, wherein the dielectric layer includes a zirconium oxide, analuminum oxide, or a combination thereof.
 8. The capacitor of claim 1,wherein the bottom electrode has a cylindrical shape or a pillar shape.9. The capacitor of claim 1, wherein the bottom electrode includes atitanium nitride.
 10. The capacitor of claim 1, wherein the dielectriclayer includes ZAZA (ZrO₂/Al₂O₃/ZrO₂/Al₂O₃) stack.
 11. The capacitor ofclaim 1, wherein the dielectric layer includes ZAZ (ZrO₂/Al₂O₃/ZrO₂)stack, HAH (HfO₂/Al₂O₃/HfO₂) stack, TiO₂/ZrO₂/Al₂O₃/ZrO₂ stack,TiO₂/HfO₂/Al₂O₃/HfO₂ stack, Ta₂O₅/ZrO₂/Al₂O₃/ZrO₂ stack orTa₂O₅/HfO₂/Al₂O₃/HfO₂ stack.
 12. The capacitor of claim 1, wherein thehigh work function interface layer has a work function of 4.9 eV orhigher.